An optical semiconductor device is known which includes optical semiconductor elements encapsulated with two or more resin layers. In this device, a first encapsulating resin, which is in direct contact with the optical semiconductor elements, is formed by dipping or potting, and the resin layers are disposed such that their refractive indexes become sequentially smaller, layer by layer, from the optical-semiconductor element side toward the outermost layer so as to have an improved efficiency of light takeout (see patent document 1).
Patent Document 1: JP 10-65220 A
However, resin encapsulation by dipping or potting has a drawback that the operation of dropping a liquid resin onto individual optical semiconductor elements in a given amount each is troublesome. Furthermore, the encapsulation of optical semiconductor elements with resin layers differing in refractive index necessitates two or more steps and is hence troublesome.